Apparatus for preventing disengagement of seal member in a booster

Abstract

A booster as may be used in a brake of an automobile is provided. Specifically, an improvement of means for sealing between a stepped tubular portion formed on the rear side of a shell and a tubular terminal end of a valve body which extends therethrough is provided. According to the invention, an annular seal member and a bearing are sequentially fitted inside the stepped tubular portion of the shell from the front side and their inner peripheral portions are disposed in sliding contact with the tubular terminal end of the valve body. A plurality of projections are formed on either end face of the seal member or the bearing which opposes each other around its outer periphery. The provision of such projections is effective to prevent the seal member from being disengaged from the step of the stepped tubular portion in the rearward direction.

What is claimed is: 
     
       1. A booster comprising: a shell including a stepped tubular portion which extends axially rearward from a rear end face of the shell and has a step formed therein, the stepped tubular portion having a greater diameter forwardly of the step,   a reciprocable valve body disposed within the shell and including a tubular terminal end which projects axially rearward through the stepped tubular portion,   a bearing disposed within the portion of the stepped tubular portion which has the greater diameter for slidably supporting the tubular terminal end of the valve body,   an annular seal member disposed within the portion of the stepped tubular portion having the greater diameter so as to be held sandwiched between the step and the bearing in sealing engagement with the tubular terminal end to provide a seal between the stepped tubular portion and the tubular terminal end of the valve body, the seal member having an end face, and the bearing having an end face facing toward the end face of the seal member in a mutually opposing relation, each of the mutually opposing end faces being defined by a radially outer region and a radially inner region; and   means for preventing disengagement of the seal member comprising a projection portion disposed on one of the mutually opposing end faces of the seal member and the bearing in the radially outer region of said one of the mutually opposing end faces for engagement with the other of the mutually opposing end faces, the radially inner regions of the mutually opposing end faces being circumferentially continuously spaced apart and out of contact with one another by a circumferentially continuous space radially extending inwardly from the radially inner side of said projection portion to the radially inner edge of at least one of said opposing end faces.   
     
     
       2. An apparatus according to claim 1 in which the bearing is fitted inside the portion of the stepped tubular portion having the greater diameter from the front side thereof and is positioned at a given axial position therein by a retainer which is disposed in abutment against the bearing, and in which the seal member comprises an annular portion having an increased wall thickness which is fitted within the portion of the stepped tubular portion having the greater diameter and is disposed in contact with the step, and a lip portion located radially inward of the annular portion and disposed for sliding contact with an outer peripheral surface of the tubular terminal end of the valve body. 
     
     
       3. An apparatus according to claim 2 in which the end face of the seal member which faces the bearing is tapered so that the radially inner region thereof projects forwardly of the radially outer region, the projection portion including a plurality of projections formed on the end face of the seal member which faces the bearing at a plurality of locations which are circumferentially spaced apart around the outer periphery thereof in the radially outer region. 
     
     
       4. A apparatus according to claim 2 in which the end face of the seal member which faces the bearing is tapered so that the radially inner region thereof projects forwardly of the radially outer region, and in which the projection portion comprises an annular projection formed on the end face of the seal member which faces the bearing around the radially outer region, said annular projection being circumferentially continuous. 
     
     
       5. An apparatus according to claim 2 in which the projection portion includes a plurality of projections formed on the end face of the bearing which faces the seal member around the radially outer region thereof at a plurality of locations which are circumferentially spaced apart. 
     
     
       6. An apparatus according to claim 2 in which the projection portion comprises an annular projection which is formed on the end face of the bearing which faces the seal member around the radially outer region thereof, the annular projection being circumferentially continuous. 
     
     
       7. A booster comprising: a shell including a stepped tubular portion which extends axially rearward from a rear end face of the shell and has a radially inward extending step, the stepped tubular portion having a portion with a greater diameter disposed forwardly of the step;   a reciprocable valve body disposed within the shell and including a tubular terminal end which projects axially rearward through the stepped tubular portion;   a bearing disposed forwardly of the step within the greater diameter portion and extending about an outer periphery of the tubular terminal end for slidably supporting the tubular terminal end of the valve body, the bearing having a greater diameter corresponding to the greater diameter of the stepped tubular portion;   an annular seal member disposed within the greater diameter portion of the stepped tubular portion, the seal member having a radially outer portion in contact with and sandwiched between the step and the bearing, and a radially inner portion extending radially inwardly from the radially outer portion in sealing engagement with the tubular terminal end to provide a seal between the stepped tubular portion and the tubular terminal end of the valve body, the seal member having an end face and the bearing having an end face facing toward the end face of the seal member in a mutually opposing relation, each of the mutually opposing end faces being defined by a radially outer face region and a radially inner face region; and   means for preventing disengagement of the seal member comprising a projection portion which is disposed on one of the mutually opposing end faces of the seal member and the bearing and extends from the radially outer face region of said one of the mutually opposing end faces so as to contact the radially outer face region of the other of the mutually opposing end faces, the radially inner regions of the mutually opposing end faces being circumferentially continuously spaced apart and out of contact with one another by a circumferentially continuous space radially extending inwardly from the radially inner side of said projection portion to the radially inner edge of at least one of said opposing end faces.   
     
     
       8. An apparatus according to claim 7 in which the projection portion includes a plurality of projections disposed on said one of the mutually opposing end faces at a plurality of locations which are circumferentially spaced apart around the radially outer region. 
     
     
       9. An apparatus according to claim 7 in which the projection portion comprises an annular projection disposed on said one of the mutually opposing end faces, the annular projection being circumferentially continuous.